Remove recordings feature, replay sessions directly, bump to 0.6.0

Recordings were just a thin named pointer over an already-captured
session's events, so the whole separate feature (recordings table, API
routes, pages, UI) is gone: any completed session can now be named and
replayed directly. Replaying no longer creates a session or duplicates
events of its own - it just bumps the source session's playCount/lastPlayedAt.

Also renames play_sessions/playSession(s) to sessions/session(s) throughout
the schema, queries, API routes, and UI for consistency, and updates the
README to match the new flow.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/(app)/sessions/page.tsx

@@ -2,7 +2,7 @@ import type { Metadata } from "next";
 import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
 import { SessionsTable } from "@/components/sessions/SessionsTable";
 import { PageNav } from "@/components/shared/PageNav";
-import { listPlaySessionsPage } from "@/lib/db/queries/play-sessions";
+import { listSessionsPage } from "@/lib/db/queries/sessions";
 import { parsePage } from "@/lib/pagination";
 
 export const dynamic = "force-dynamic";
@@ -14,7 +14,7 @@ export default async function SessionsPage({
   searchParams: Promise<{ page?: string }>;
 }) {
   const page = parsePage((await searchParams).page);
-  const { items: sessions, pageSize, total } = await listPlaySessionsPage(page);
+  const { items: sessions, pageSize, total } = await listSessionsPage(page);
 
   return (
     <div className="flex flex-col gap-6">